IGCSEPhysicsEdexcelExam Questions8. AstrophysicsCosmology

Cosmology (Edexcel IGCSE Physics)

Exam Questions

2 hours15 questions
Easy
Medium
Hard
1a2 marks

State what is meant by redshift.

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1b1 mark

Light from a distant galaxy appears to have been redshifted.

Which of the following rows correctly describes the change in the frequency and wavelength of the light when it is observed on Earth?

  Frequency Wavelength
A Decreases Decreases
B Increases Decreases
C Decreases Increases
D Increases Increases

    Choose your answer

    1c4 marks

    The diagram shows two people observing the same light source, which is in motion. The light is moving to the right.

    8-3-1c-e-redshift-labelling-light-bulb-sq-igcse

    Complete the boxes on the diagram with words or phrases from the list below.

     
    higher frequency       lower frequency       phase difference       wavelength       blueshift       relative motion       star       redshift

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    2a3 marks

    State what is meant by the Doppler effect.

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    2b2 marks

    Name two properties of waves which are observed to change due to the Doppler effect.

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    2c2 marks

    An object is moving away from a stationary observer whilst emitting a steady sound wave.

    (i)
    State the property of the sound wave which increases.
    (1)
    (ii)
    State the property of the sound wave which decreases.
    (1)
    (iii)
    State the property of the sound wave which remains constant.
    (1)

    How did you do?

    2d7 marks

    The following passage is about the Doppler effect.

    Complete the following sentences by circling the correct words: 

    When a source starts to move away from / towards the observer, the wavelength of the wave broadens. 

    For sound waves, sound therefore appears at a higher / lower frequency to the observer. 

    For light waves, the light shifts towards the blue / red end of the electromagnetic spectrum due to its lower / higher frequency. 

    When a source starts to move away from / towards the observer, the wavelength of the wave shortens. 

    For sound waves, sound therefore appears at a higher / lower frequency to the observer. 

    For light waves, the light shifts towards the blue / red end of the electromagnetic spectrum due to its lower / higher frequency. 

    This is because blue / red light has a longer wavelength than blue / red light.

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    3a1 mark

    Light from distant galaxies appears red-shifted to observers on Earth.

    Which of the following ideas does this provide evidence for?    

    1. The Big Bang Theory
    2. The Universe is expanding
    3. Distant Galaxies are moving both towards us and away from us

    • 1 only

    • 1 and 2

    • 2 only

    • 1, 2 and 3

    Choose your answer

    3b4 marks

    This passage is about redshift.

    Complete the following sentences by filling in the correct words in the gaps. Use words from the box below:

    stretch out     slower     expanding     moving towards     red

    receding     faster     black hole     doppler    blue
     

    After the discovery of Doppler redshift, astronomers began to realise that almost all the galaxies in the universe are ........................ .

     
    This led to the idea that the universe must be ........................ .

     
    This caused the light waves to ..................... ..................... as they travel through space, shifting them towards the ........................ end of the spectrum.

     
    The more shifted the light from a galaxy is, the ........................ the galaxy is moving away from Earth.

    How did you do?

    3c6 marks

    The following passage is about the start of the universe.

    Complete the passage using words in the box below.

     
    explosion        faster        expand        Big Bang        heats        hot        Big Crunch        shrinks        cools

     

    Around 14 billion years ago, the Universe began from a very small region that was extremely ............... and dense.

    Then there was a giant explosion, which is known as the ............... ................

    This caused the universe to ............... from a single point to form the universe today.

    Each point expands away from the others and the universe ............... due to this.

    This is seen as galaxies move away from each other, and the further away they are the ............... they move.

    As a result of the initial ..............., the Universe continues to expand.

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    4a1 mark

    Which of the following statements provides evidence that the universe is expanding?

    • light from galaxies is red shifted

    • nuclear fusion occurs in stars

    • many stars have orbiting planets

    • stars form from large clouds of dust and gas

    Choose your answer

    4b1 mark

    An astronomer observes that light from a galaxy has been shifted towards the blue end of the spectrum.

    What can be deduced about the motion of the galaxy from this observation?

    • the galaxy is moving towards the Earth

    • the galaxy is moving away from the Earth

    • the galaxy is not moving relative to the Earth

    • the galaxy is expanding

    Choose your answer

    4c1 mark

    The diagram shows some wavelengths that were observed using light from a source in a laboratory:

    8-3-4c-e-hydrogen-spectrum-redshift-mcq-igcse

    The same wavelengths of light observed from a distant galaxy were found to be redshifted.

    Which of the following statements about the redshifted light is correct?

    • all the lines move towards the 'short λ' side by different amounts

    • all the lines move towards the 'long λ' side by different amounts

    • all the lines move towards the 'short λ' side by the same amount

    • all the lines move towards the 'long λ' side by the same amount

    Choose your answer

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    5a3 marks
    (i)
    State the name of the theory that suggests that the Universe started with a massive explosion.
    (1)
    (ii)
    State the names of two observations that support this theory.
    (2)

    How did you do?

    5b3 marks

    The table below contains statements about this theory.

    Put ticks (✓) in the boxes to show which statements that are correct.

     
    Statement Correct (✓)
    The Universe began 14 million years ago  
    There was a giant explosion known as the Big Bang  
    This caused the Universe to expand from a single point  
    It heated as it expanded to form the Universe today  
    Each point in the Universe expands away from the others  
    So, the further away galaxies are the slower they are moving  

     

    How did you do?

    5c5 marks

    The table below shows statements of evidence for the theory.

    Put ticks (✓) in the boxes to indicate whether the statement is evidence from galactic redshift or CMB radiation.

     
    Statement Evidence from Galactic Redshift Evidence from CMB Radiation
    Astronomers discovered radiation in the microwave region of the electromagnetic spectrum coming from all directions    
    Radiation is in the microwave region because the radiation initially from the Big Bang has redshifted as the Universe has expanded    
    Observations of light spectra from supernovae indicate that distant galaxies are receding    
    Galaxies that are further away are moving faster, as their distance is proportional to their speed    
    Light spectra from distant galaxies show that light is redshifted which is evidence of the Universe expanding    

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    1a3 marks

    Explain the term galactic redshift.

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    1b2 marks

    Explain why galactic redshift provides evidence to support the Big Bang theory.

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    1c4 marks

    Describe and explain what can be deduced from the cosmic microwave background radiation (CMBR).

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    2a1 mark

    A train is moving towards a stationary observer. The train sounds its horn. 

    What are the correct changes in frequency, wavelength and pitch of the horn as heard by the observer?

     
     

    frequency

    wavelength

    pitch

    A.

    		 higher shorter higher

    B.

    		 higher shorter lower

    C.

    		 lower shorter lower

    D.

    		 lower longer higher

      Choose your answer

      2b1 mark

      Which of the following statements about the Doppler effect is correct?

      • When a galaxy moves towards the Earth the spectral absorption lines observed will have a longer wavelength

      • When a car starts to move away from an observer, the sound from the exhaust appears at a lower frequency to the observer than the driver

      • When a train moves towards a station, it's horn will sound lower to the passengers on the platform compared to the passengers in the train

      • Light from a star moving towards the Earth is redshifted

      Choose your answer

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      3a4 marks

      In the laboratory on Earth, hydrogen emits a spectral line that is measured by an observer to have a wavelength of 400 nm.

      The same spectral line is emitted by a galactic source that is moving away from Earth at speed of 6 × 107 m/s.

      The speed of light is 3.0 × 108 m/s.

      Calculate the wavelength of the same spectral line from the galaxy as measured by the observer on Earth. 

      Use the equation:

      fraction numerator straight capital delta lambda over denominator lambda subscript 0 end fraction equals v over c

       

      wavelength = ............................ nm

      How did you do?

      3b4 marks

      A spectral line is observed at 530 nm in the laboratory. The same spectral line is observed in a galaxy which is receding from Earth at a wavelength of 535.3 nm.

      Calculate the relative speed at which the galaxy is moving away from the Earth.

      relative speed of the galaxy = ......................................... m/s

      How did you do?

      3c1 mark

      Which of the following statements is true about redshift?

      • Redshift led to the idea that galaxies are expanding

      • A greater redshift means a faster speed of recession

      • Redshift shows a few of the galaxies in the universe are moving away from a single point

      • Redshift causes electromagnetic waves to change frequency and speed.

      Choose your answer

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      4a3 marks

      The Big Bang theory attempts to explain the origin of the Universe.

      Describe the main ideas of the Big Bang theory.

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      4b4 marks

      State and explain the two pieces of evidence which support the Big Bang Theory of the origin of the Universe.

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      4c3 marks

      State and explain what type of electromagnetic radiation the CMBR will change into over the next few billion years.

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      4d2 marks

      Suggest why our understanding of the beginning of the Universe is just a theory.

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      5a5 marks

      Light emitted from a distant galaxy is measured on Earth to have a wavelength lambda of 400 nm. The same wavelength is measured in the laboratory to have a wavelength lambda subscript 0 of 300 nm.

      The speed of light in space, c = 3.00 × 108 m/s.

      (i)
      Calculate the change in wavelength between the emission of light from the galaxy to its measurement on Earth.
      (2)
        

      change in wavelength = .......................... m

      (ii)
      Calculate the speed at which the galaxy is moving relative to the Earth.
      (3)
       

      relative speed of the galaxy = ................................. m/s

      How did you do?

      5b5 marks

      A nearby star is observed in relation to a distant galaxy. Both the nearby star and the distant galaxy emit light with a wavelength of 450 nm.

      When the light from the star arrives on Earth its wavelength is unchanged. When the light from the distant galaxy arrives on Earth, it appears to have been redshifted.

      The galaxy is observed to be moving away from the Earth with a velocity of 2.0 × 104 m/s.

      Calculate the wavelength of the light from the galaxy when it arrives on Earth.

      wavelength observed on Earth = ............................. nm

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      1a3 marks

      Hydrogen is an element of particular interest to astronomers, as it can emit visible light waves.

      A lot of useful information can be obtained by measuring the wavelength of the emitted light from the hydrogen in distant galaxies and comparing them to a laboratory sample of hydrogen. Some sample data is shown in the table.

      The detected wavelengths from the galaxies are different from the detected wavelength from the laboratory sample because of the Doppler effect.

        Wavelength in nm
      Laboratory sample 486.14
      Galaxy X 486.40
      Galaxy Y 484.85

      Galaxy X and galaxy Y are both moving relative to Earth. 

      Compare the motions of galaxy X and galaxy Y relative to Earth.

      How did you do?

      1b4 marks

      Use data from the table to calculate the speed of galaxy Y relative to Earth. 

      Speed of light, c = 3.0 × 108 m/s

      speed of galaxy Y = ................................... m/s

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      2a1 mark

      An astronomer analyses the light from two distant galaxies, S and T.

      One of the spectral lines in the spectrum observed from galaxy S has a wavelength of 610 nm. The same spectral line has a wavelength of 590 nm when measured in the laboratory.

      The speed of light is c = 3.0 × 108 m/s

      What is the speed of galaxy S in terms of c?

      • 0.0327 c

      • 0.0339 c

      • 0.967 c

      • 1.000 c

      Choose your answer

      2b3 marks

      Galaxy T is twice as far away from the Earth as galaxy S. 

      (i)
      Suggest how the speed of galaxy T relates to the speed of galaxy S.
      (1)
      (ii)
      Suggest a value for the change in wavelength of light from an identical star in galaxy T when the light arrives at the Earth.
      (2)

      How did you do?

      2c4 marks

      Explain how comparing the speeds of the two galaxies provides evidence for the Big Bang theory. 

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      3a1 mark

      In 1929, the astronomer Edwin Hubble showed that the universe was expanding.

      He observed that the spectra of light emitted from distant galaxies were shifted towards the red end of the spectrum. He found that the further away the galaxy, the further the light was shifted towards the red end of the spectrum compared to closer galaxies.

      Two wavelengths of hydrogen, 434 nm and 486 nm, are measured in a laboratory, as shown in the diagram.

      8-3-q3a-5-h-hydrogen-spectrum-lab-mcq-igcse

      The same wavelengths of hydrogen are measured from four different galaxies.

      Which of the galaxies is the farthest away from Earth?

      8-3-q3a-1-h-hydrogen-spectrum-a-mcq-igcse

      8-3-q3a-2-h-hydrogen-spectrum-b-mcq-igcse

      8-3-q3a-3-h-hydrogen-spectrum-c-mcq-igcse

      8-3-q3a-4-h-hydrogen-spectrum-d-mcq-igcse

        Choose your answer

        3b1 mark

        Following on from his work on galactic redshift, 'Hubble's Law' was established, which states

        The recessional velocity, v, of a galaxy is proportional to its distance, d, from Earth

        Hubble's Law can be expressed as an equation

        v space equals space H subscript 0 d

        Where H subscript 0 is a constant known as the 'Hubble constant'. 

        A spectral line corresponds to a wavelength λ1 in the laboratory. The same spectral line observed in the spectrum of a receding galaxy corresponds to a wavelength λ2.

        The speed of light in a vacuum is c.

        Which of the following is the correct expression for the Hubble constant H subscript 0?

        • H subscript 0 space end subscript equals space fraction numerator c open parentheses lambda subscript 2 space end subscript minus space lambda subscript 1 close parentheses over denominator d space lambda subscript 1 end fraction

        • H subscript 0 space end subscript equals space fraction numerator c lambda subscript 1 over denominator d space open parentheses lambda subscript 2 space end subscript minus space lambda subscript 1 close parentheses end fraction

        • H subscript 0 space end subscript equals space fraction numerator c lambda subscript 2 over denominator d lambda subscript 1 end fraction

        • H subscript 0 space end subscript equals space fraction numerator c lambda subscript 1 over denominator d lambda subscript 2 end fraction

        Choose your answer

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        4a3 marks

        The Doppler effect can be used to determine whether a star is moving away from or towards the Earth. 

        State and explain what is meant by 'Doppler effect' in this context.

        How did you do?

        4b6 marks

        In a laboratory, hydrogen is found to emit light of wavelength 656.61 nm. The spectrum of a star observed on Earth is found to have the same line in the spectrum shifted to 656.68 nm.

        The speed of light is c = 3.0 × 108 m/s

        (i)
        Calculate the speed at which the galaxy is moving relative to the Earth.
        (4)
         
        speed of the star = ................................... m/s
        (ii)
        Explain whether the star is moving towards or away from the Earth.
        (2)

        How did you do?

        4c3 marks

        A second spectral line is observed at 567.34 nm in the laboratory. 

        Determine the frequency of the spectral line from the star, as observed on Earth.

         
        Frequency = ......................................... Hz

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        4d2 marks

        Explain the effect on the colour of light from the star if it were travelling in the opposite direction.

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        5a3 marks

        The Big Bang theory suggests that the Universe is approximately 14 billion years old.

        Describe the evolution of the Universe from the Big Bang until the present day. 

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        5b5 marks

        Describe the evidence that supports the Big Bang theory. 

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